linux-kernel - [PATCH] arm64: topology: Don't support AMU without cpufreq

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Message-Id: <a710fc4e4e0f1d2e561320130b99bcb5167d73b4.1594277563.git.viresh.kumar@linaro.org>
Date:   Thu,  9 Jul 2020 12:22:45 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Ionela Voinescu <ionela.voinescu@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [PATCH] arm64: topology: Don't support AMU without cpufreq

The commit cd0ed03a8903 ("arm64: use activity monitors for frequency
invariance"), mentions that:

  "if CONFIG_CPU_FREQ is not enabled, the use of counters is
   enabled on all CPUs only if all possible CPUs correctly support
   the necessary counters"

But that's not really true as validate_cpu_freq_invariance_counters()
fails if max_freq_hz is returned as 0 (in case there is no policy for
the CPU). And the AMUs won't be supported in that case.

Make the code reflect this reality.

Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
 arch/arm64/kernel/topology.c | 19 +++----------------
 1 file changed, 3 insertions(+), 16 deletions(-)

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 0801a0f3c156..b7da372819fc 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -187,14 +187,13 @@ static int validate_cpu_freq_invariance_counters(int cpu)
 	return 0;
 }
 
-static inline bool
-enable_policy_freq_counters(int cpu, cpumask_var_t valid_cpus)
+static inline void update_amu_fie_cpus(int cpu, cpumask_var_t valid_cpus)
 {
 	struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
 
 	if (!policy) {
 		pr_debug("CPU%d: No cpufreq policy found.\n", cpu);
-		return false;
+		return;
 	}
 
 	if (cpumask_subset(policy->related_cpus, valid_cpus))
@@ -202,8 +201,6 @@ enable_policy_freq_counters(int cpu, cpumask_var_t valid_cpus)
 			   amu_fie_cpus);
 
 	cpufreq_cpu_put(policy);
-
-	return true;
 }
 
 static DEFINE_STATIC_KEY_FALSE(amu_fie_key);
@@ -212,7 +209,6 @@ static DEFINE_STATIC_KEY_FALSE(amu_fie_key);
 static int __init init_amu_fie(void)
 {
 	cpumask_var_t valid_cpus;
-	bool have_policy = false;
 	int ret = 0;
 	int cpu;
 
@@ -228,18 +224,9 @@ static int __init init_amu_fie(void)
 		if (validate_cpu_freq_invariance_counters(cpu))
 			continue;
 		cpumask_set_cpu(cpu, valid_cpus);
-		have_policy |= enable_policy_freq_counters(cpu, valid_cpus);
+		update_amu_fie_cpus(cpu, valid_cpus);
 	}
 
-	/*
-	 * If we are not restricted by cpufreq policies, we only enable
-	 * the use of the AMU feature for FIE if all CPUs support AMU.
-	 * Otherwise, enable_policy_freq_counters has already enabled
-	 * policy cpus.
-	 */
-	if (!have_policy && cpumask_equal(valid_cpus, cpu_present_mask))
-		cpumask_or(amu_fie_cpus, amu_fie_cpus, valid_cpus);
-
 	if (!cpumask_empty(amu_fie_cpus)) {
 		pr_info("CPUs[%*pbl]: counters will be used for FIE.",
 			cpumask_pr_args(amu_fie_cpus));
-- 
2.25.0.rc1.19.g042ed3e048af